This answer to Making food last for a large group made me realize that using the zombies as a source of resources is pretty much never covered by genre pieces even when it is essentially a siege situation.
What ways can the besieged find to use the (“killed” for good) zombies as a source of food and other resources? Simply having them be edible like any game animal is too easy: they will be hazardous (rotten or infectious) if treated casually.
In all cases, suppose that cooking properly will take care of infection.
But the skeletal muscles are rotten in the classic zombie: Perhaps you harvest just the (high-calorie) bone marrow, which is not rotted. More generally, some parts may still be edible, depending on the age of the zombie.
But all the “off” meat does not go to waste. Many animals can eat meat that humans can’t or won’t, and there are other animals that specialize in eating carrion. The survivors might capture the scavengers that are doing well in the current situation, and breed them for meat. This makes me realize that it’s not just a zombie-human apocalypse, but will be a hyena and vulture apocalypse too! If the animals are affected in the same way, things will be even more interesting especially with flying animals involved.
If hyenas and coyotes are not infected in the same way as humans, they might make good tools for fighting the zombies!
Now feeding meat animals is a rapid and concentrated source of calories but is inefficient, producing only a percentage of what went through the process. Growing crops is more efficient. So the zombie remains ought to be composted and used to grow vegetables, rice, and beans. This takes a large amount of territory to be under the people’s control, and more time.
But zombies don’t bother crops, right? So the land need not be full-time secured. Farmers would employ the domesticated coyotes or dogs‡ to be on the lookout around the farm and the group of workers in particular.
As for resources other than calories, you have many of the usual animal parts: bone, sinew, leather. Many knives, weapons, and farming implements will be made from zombie bones.
‡ About dogs: I made a distinction above between meat that's just a bit off and can be eaten by many animals (but not humans), and truly rotted meat. Rats and dogs fall in the first category. Carrion feeders will eat stuff up to the point of already being compost.
So dogs may be good for defending against zombies without getting sick, and may munch on the not-too-decayed specimens and bones.
Zoönosis※: Generally diseases are species-specific. So by default we expect animals will not be infected by zombies in the same way as humans. Doing so would make for a very different story with zombie mosquitoes spreading the infection, and beetles infecting the entire ecosystem in short order.
But you may have some animals infected in some ways. In particular, if the zombie virus came from an animal reservoir, then those specific animals will be asymptomatic carriers or get ordinary sick from it. Now if zombism came from a mutation of rabies then it might present as rabies in canids and bats. That means people will have to use animals other than coyotes and hyenas: would they use vultures perhaps?
※ I use the diaeresis to emphasize that the two os don’t merge together like in zoo. It’s like coördinate.
This really depend on zombie type;
Regardless of the trigger for Zombiefication (voodoo or virus) human cannibalism is a Very Bad Idea™.
The fatal prion malady kuru (shaking death) wiped out many participants of the last recorded cannibal feast by the Fore tribe in Papua New Guinea. Other malformed prion maladies are also a threat. Kuru is suspected of having a 50 year incubation period. Actually that's the only problem I can find a reference for right now.
So WARNING: do not eat the brains.
Cannibalism makes it easier for pathogens to cross the blood/brain barrier (I think - again no reference).
Zoonosis becomes an issue if the devoured body already has the disease. But consuming cooked human flesh is a lower risk behaviour than most other bodily fluid exchange. Wikipedia lists 34 types of body fluids.
According to my industrial chemist sister, the gut is such a toxic environment that food and drug safety standards (for compounds) are lower than cosmetics safety standards. In the sense that companies can put stuff in food and drugs that is banned from going on your face. Cosmetics standards also have lower absolute quantities and concentrations of active ingredients.
Now once TB, Rabies, Leprosy, ebola or the other 18 Zoonosis diseases are in the human population, I wouldn't want to consume that meat.
A couple options:
That last one might need some explanation. Perhaps tendons are discovered to have a high tensile strength. Bone meal or shards might make a new form of concrete. Brain squeezings could be the best wood preservative ever. Rendered flesh might be an amazing rubber replacement. Further, the use of these materials might ward off attacking hordes.
Other answers have thoroughly described the ways in which eating zombies directly is a bad idea - risk of infection, lack of edible meat/nutrients, cannibalism...
However, we don't need to or want to eat the zombies. We just want food and resources. You haven't described exactly what sort of zombie your setting contains, but they are typically:
You may be able to fool them into generating resources like draft animals. They could be chained back and walk forward on a treadmill towards some brains harvested from an animal or another zombie (or just a picture of brains), shuffling forwards and generating power. Or perhaps you could convince them that if they braved the zombie-infested supermarket and returned with a certain object (they aren't vulnerable to infection, after all), stood guard in a watchtower (with appropriate testing and redundancy, of course), or pulled a plow through a field (ensuring that the final product isn't contaminated with the virus), you would give them something they wanted.
I help run a fantasy haunted adventure every year in October. One year, our story line was a post-apocalyptic landscape full of zombies. Modern tech manufacturing was dead, but it's amazing what you can build out of zombies. They don't die. So...
If I were a leader of some enclave I would assemble a crew who would:
Other possible uses:
Eating zombies? Nice try.. now convince anyone to do it.
As others have mentioned, this depends a lot on what the rules behind turning into a zombie are. Meaning, this could change from world to world.
If becoming a zombie it is the result of a pathogen, then the nature of the infection will dictate the feasibility of zombies becoming a source of food.
Consider the core options in a world infested with zombies:
Depending on how the agent of infection is spread and its fortitude, it might be possible that certain animals, plants and insects could be able to withstand the contamination and detoxicate the food or water. Conversely, some animals, plants and insects could increase the potency of the agent potentially mutating it into something worse. This, again, depending on how that particular world works.
If becoming a zombie is the result of a curse or magic like in the film The Serpent and the Rainbow, the rules of what is needed, how it affects the body and how it is transmitted will determine the edibility of any zombified beings.
In the particular case of the film mentioned, it appears that a drug is used to produce the desired effect. Some drugs must be injected directly to the blood stream for them to work, while others have to be ingested, this will also become a factor on edibility. Some components can be eaten without producing the effect, so in that case it could be safe.
More magical realms would require additional analysis on what happens to cursed or enchanted beings that get eaten. Interestingly enough, despite all the fairy tales there is little exploration on this aspect of magic.
However, worlds with magical-based zombies might have an edge if there are spells or potions which revert them back to their former selves. Notice that this might differ a little from an uncontrolled outbreak scenario, since magical zombies tend to be more controlled and those who tame them have developed means to keep themselves from becoming zombies. Even the film mentioned shows that zombies are easily manipulated by those who turn them.
If becoming a zombie is the result of a parasite (like real life ant-zombies infected by a fungus) then it will depend on the characteristics of the parasite itself. In the particular case of the fungus that infects the ants, the parasite only attacks a particular species, which might make it relatively safer to consume (if the zombified animal was not a human, of course).
Like other parasites, it is possible to use methods to cook such meat by ensuring the death of the parasite before consuming the food; however, how safe it really is can only be determined by how the parasite reproduces and propagates.
An example of a work of fiction where zombification has been treated as a parasite with very specific rules on its propagation would be "Higurashi Outbreak". Animals are not covered in that particular scenario, so it would be safe to consume any meat produced by an animal, given other qualities of the parasite explained in that film.
With that in mind, everything really comes down to the rules of the particular world which is under a zombie siege. A work of fiction that does address food and resources in a zombie post-apocalyptic world is the web comic Zombie Ranch. In this particular instance, animals and humans can become zombies and eating zombies is safe, despite the taste. In this world, humans are forced to become vegetarians. Additionally, zombie blood is not contagious and they can be used to produce medicines that extend the life of the living and other products.
Having said that, zombies could be used for labor depending on how sturdy they are in the world in question. They could also be used for theoretical perpetual motion machines, these two under the provisions of the rules of the world, since zombies that might not consume flesh (or brains) might eventually lose energy, become inactive and break-down.
Despite the kind of zombie, they could be leveraged for hunting (like how hunt dogs are used) but this would require to have a certain degree of control over the zombies, which would vary from reality to reality. Additionally, depending on how the zombification process happens, it might not be a good idea to risk to infect your food by performing said actions.
Back to the issue of having a safe way to eat zombies. If we were to assume all the worlds to which this question would apply are similar to ours, then there is one simple answer: Pasteurization.
Pasteurization would address zombies that have been turned due to a pathogen and parasites, since it is a process which kills microbes (bacteria) in foods and drinks. If you were also to assume that eating beings that have been exposed to magic as a non-issue (meaning that magic would not cause any damage to those consuming magically treated food) then, that addresses the main issue.
Pasteurization is easy enough to perform without a lot of technology, since it was discovered in 1864 by Pasteur who noticed that heating beer and wine would kill most of the bacteria in it, leading to a process that achieves eliminating pathogenic microbes. Since this process is used widely in food processing industries and the dairy industry, it is not a stretch that ranchers might be able to survive a zombie apocalypse by applying knowledge of food preservation that they already possess, making a "zombie ranch" more plausible.
Now, on to the other aspect of the question: resources. Being able to use the zombies as other resources would depend on several factors such as the infrastructure that is left in the world after an outbreak and the properties of the "undead" creatures, as previously discussed; however, there are similarities in all worlds where there is a concept of a zombie which is the usage of these undead fiends against other humans (It comes down to weaponizing them).
Louis Pasteur, saving the multiverse from zombie apocalypses since 1864.
If I was stuck in a building with limited resources and I was currently being besieged by zombies, I would go Zombie Fishing. With some rope and if lucky some type of large hook like object I would lower it off the roof or out a high window and try to snag one zombie. One I have one I would pull it up just high enough to bludgeon it and then pull it in. IF by change more than one zombie started climbing my line I would cut it free and try again.
For the most part I imagine zombies are inedible. Maybe you could cook them, autoclave them, char them but personally I wouldn’t risk it.
What Zombie fishing would do is supply me with resources. These are not just walking corpses, these were other survivors hording supplies. That zombie with the backpack, he is the one you want to aim for while zombie fishing. Yes he could have been an unlucky student on his way to school, or he could have been that guy who nabbed the last can of soup from the store.
As mentioned by other Zombies could be disassembled, skin could be tanned and used as leather, bones could be used as building material. Lukbl mentioned burning them and using the ash as fertilizer. You can add ash to a compost, but by itself it is probably not as usefully as a fertilizer as compost. On the other hand it is better than trying to grow something in plane sand.
One possibility is to create a partial cure for zombification, one which restores the body but not the mind. You could use this medicine or method to restore the zombies to edible flesh.
This could also allow for interesting scenarios, such as a divide between those with the resources to turn zombies into food and those without.
Because humans are unfortunately not breed for having the best kind of meat anyway.
So eating them would be like eating humans, last resort for protein source. Humans eat humans when they don't have anything else, so the same would be applied to zombies.
BUT - the zombie meat would have one, general, disadvantage over human meat. It could be dead/killed weeks before you would like to treat them like food.
BUT - the essence of zombie existing in the first place MUST be that the dead meat don't spoil, rotten or is affected in any kind by regular oxidation.
SO - just give a handful of spices and serve with a nice chianti and fava beans.
Eating zombies is nasty. Using them on a treadmill as perpetual motion machines is zany.
But you could burn them as fuel and power a steam engine. I could imagine apocalypse survivors conducting routine burns of the zombies which had accumulated in their trenches, then running out of firewood / coal for their own heat and power, then thinking... First world humans are pretty greasy and when they dry out as zombies will be even greasier. Got lemons, make lemonade. This would work for any of the 3 zombie types listed above.
There is precedent for using animals as fuel: oily freshwater sturgeon were netted, stacked and dried, then used to fuel steamboats in the early 1800s. There was a whole industry dedicated to catching and processing whales for fuel.
One drawback: as regards a fictional work, in my mind this approach is tainted by a similarity to the Auschwitz ovens. Maybe it is just how I envision it or because I am old. The writer will need to take some care in how it is depicted.
To answer this question we must know WHAT type of zombie you are referring to.
Virus Zombie?
Cursed Zombie?
Fungal Zombies?
Since you didn't include these in your question I guess I'll have to describe ways to eat each one.
Viral Zombies: If you are trying to eat a zombie that is infected with a "Zombie Virus" then I suggest that you rapidly freeze and defreeze the zombie meat (to decrease the chances of viral transmission), If your population does not have access to a device that freezes things then I suggested that you roast it over an open fire several times).
Cursed Zombies: the reason for these zombies coming back from the dead is due to a curse that has been placed on that individual. If so I reccomend roasting the flesh over an open fire ONE time (since this zombie's flesh is not contaminated with a zombification virus. Note: despite not containing a virus this type of zombie flesh contains various bacterium which cause illness and disease).
Fungal Zombies: Since this (former) person became "zombified" due to exposure to a brain consuming fungal infection then we can deduct that the rest of the body is safe to eat (unless the fungus is in multiple areas of the body, in which case you should forgo eating Zombie), If the the fungus is ONLY in the brain then I suggest you cut off all of the limbs and roast each one individually)
